1. Field of the Invention
The present invention relates to a multi-check metering method for metering the weight of a raw material by using a plurality of load cells, which are preferably provided one upon another, to enable every metering operation to be performed with multiple check kept thereon, thereby achieving secure metering, and it also relates to a metering device for carrying out said method.
2. Prior Art
Conventionally, in a process of manufacturing pharmaceutical preparations, a plurality of drugs as raw materials are mixed together. When the respective drugs are to be weighed, they are weighed twice by a metering unit. For example, a primary metering unit is provided midway along the convey line of the raw material. The raw material fed From the convey line is placed on the primary metering unit to measure its weight. When the raw material so weighed is to be loaded into a mixing tank and mixed therein, the weight of this raw material is measured again by a secondary metering unit with which the mixing tank is provided.
In this manner, the multiple check on the weight of the raw material used is performed by the primary and secondary metering units to prevent an abnormality of the metering units, an erroneous amount of the raw material loaded, or the like.
However, the above metering method raises the Following problems.
More specifically, according to the above metering method, at least two metering units in total are required for the raw material convey line and the mixing tank. In this case, since other units have been mounted on the manufacturing line of the pharmaceutical preparations, spaces for installing the metering units on this line cannot easily be obtained, thus making it difficult to install the metering units on said line.
When two metering units are installed, the number of times of the operation for checking the weight of the raw material is increased in the manufacturing process of the pharmaceutical preparations whereby operations in the manufacturing process are made cumbersome.
Furthermore, when an abnormality occurs in either metering unit, the disorder will be recognized or appreciated at the time of metering the raw material by the secondary metering unit which is the final one in this case. Therefore, undesirable preparations may be made in the mixing tank.